In which of the rulers' reigns the billon currency seems to have nearly entirely replaced silver coinage

In which of the following rulers’ reigns the billon currency seems to have nearly entirely replaced silver coinage?

Alauddin Khalji:

Alauddin Khalji was a ruler of the Delhi Sultanate in India during the 13th century.
He is known for his military campaigns and for expanding the territory of the Sultanate.
He is also remembered for his efforts to centralize the government and for his strict legal code, which was known for its severity.
Despite his successes, Alauddin Khalji is also remembered for his brutality and for the way he treated his subjects, many of whom suffered under his rule.

Muhammad Tughlaq:

Muhammad Tughlaq was a ruler of the Delhi Sultanate in India from 1325 to 1351.
He was known for his ambitious and sometimes controversial policies, including his attempts to move the capital from Delhi to Daulatabad and to introduce token currency.
He also implemented a number of social and economic reforms, including the construction of roads, wells, and schools. However, his policies often faced resistance and were not always successful, leading to a decline in the power and prosperity of the Sultanate during his reign.
Despite his controversial rule, Muhammad Tughlaq is remembered as an intelligent and ambitious leader who tried to modernize and reform the Delhi Sultanate.

Firuz Shah Tughlaq :

Firuz Shah Tughlaq was a ruler of the Tughlaq dynasty in India during the 14th century.
He was known for his military campaigns and for his efforts to bring about social and economic reforms in his kingdom.
Firuz Shah was also a patron of the arts and sciences, and he established several institutions for the promotion of learning and scholarship.
He is remembered for his benevolent rule and for his efforts to bring about unity and stability in his kingdom.
He sat on the throne after the death of Muhammad bin Tughluq.
The long reign of Firoz Shah Tughlaq seems to have established his coinage as a popular medium of exchange. Firuz Shah Tughlaq issued coins in gold, silver, copper, and billon.
Gold, copper, and billon coins issued by him are common, but his silver coins are rare.
During his reign, there was a shortage of silver coins in circulation and hence the billon currency seems to have nearly entirely replaced silver coins.

Balban :

Balban was a Turkish ruler who ruled the Delhi Sultanate in India during the 13th century.
He was known for his strict and effective rule, as well as his efforts to suppress the rebellion and bring order to the kingdom.
Balban was also a patron of arts and literature and helped to establish the city of Delhi as a cultural and intellectual center.
Despite his successes, Balban faced several challenges during his rule, including invasions from the Mongols and internal conflicts with other nobles. He died in 1287, and his legacy remains an integral part of Indian history.

Under Firuz Shah Tughlaq‘s reign, the billon currency seems to have nearly entirely replaced silver coinage