Consider two local banks. Bank A has $89$ loans$$ outstanding, each for $$$$1\mathrm{.}2$million$,$ that it expects will be repaid today. Each loan has a $7\%$ probability of$$ default, in which case the bank is not repaid anything. The chance of default is independent across all the loans. Bank B has only one loan of $$$$106\mathrm{.}8$ million$$ outstanding, which it also expects will be repaid today. It also has a $7\%$ probability of not being repaid.$$ Calculate:

c$.$ The standard deviation of the overall payoff of Bank A$.$

d$.$ The standard deviation of the overall payoff of Bank B$.$