for loop. C programming language

A capacitor discharges with time with the charcteristic of the series {50, 25, 12.5, 6.25.......}. If the intial charge of the capacitor is 50 V at time = 0 and each element in the array represent the voltage across the capacitor with interval of 1 second. Create a program that will indentify the voltage across the capacitor at t = 20 seconds given the said conditions. Store the value to a variable. Use a function aside from main function that does not return a value. See attached table in the instructions for additional requirement