Anyone know the middle question ?

The vet charges $45 for an office visit and $10 for each vaccination your dog needs. write an eaquation

11. a particular type of cell doubles in number every hour. which function can be used to find the number of cells present at the end of h hours if there are initially 4 of these cells? a. n = 4 ()" b. n = 4(2)" c. n = 4 + (2)" din = 4 +"

Can someone me out here number 4 plz