Radioactive Substance A radioactive substance with a half-life of 32 hours at t = 0. Find the number of time elapsed when:
a. 1/64 of this amount remains after t=0.
b. Only 17 grams remain, if there are 2176 grams at t=0.
c. Only 23 grams remain, if there are 736 grams at t=0.