how do I solve a and b? please show work.

S. lactis is a bacteria that can double every 210 minutes when grown in a lactose broth under ideal circumstances. If a sample of 17 of these bacteria is allowed to grow in these ideal circumstances, answer the following (a) Find an equation for a model for the number of bacteria S after n 210-minute intervals have passed 17(12)" x (b) Estimate the number of bacteria present after 7 hours bacteria Sin