Given the variables cost_per_share and number_of_shares, calculate the total amount of a stock purchase by multiplying the number of shares by the cost per share. Store your result in the variable amount. Hint: this should be just one line of code! Here is an example console session demonstrating how we will test your code (where source(...) represents us sourcing / running your solution):

> cost_per_share = 27.125 > number_of_shares <- 500 > source(...) > amount [1] 13562.5