(a) Following a radiation dose of 6 Gy, a clonogenic assay revealed that 30 colonies arose from an initial cell population of 2,000 cells. When 100 unirradiated cells were assayed for clonogenic survival, 60 colonies grew. What is the percent survival following the 6 Gy dose? 

(b) If 10⁸ cells were irradiated according to single-hit kinetics so that the average number of hits per cell is one, how many cells would survive?