Solve the Variation Problem

Solve the variation problem.
-The voltage across a resistor is jointly proportional to the resistance of the resistor and the current flowing through the resistor. If the voltage across a resistor is 72 volts for a resistor whose resistance is 9 ohms and when the current flowing through the resistor is 8 amperes, find the voltage across a resistor whose resistance is 7 ohms when the current flowing through the resistor is 6 amperes.

A) 54 volts
B) 42 volts
C) 56 volts
D) 48 volts