Calculate $($a$)$ Average quarterly cash flow

$($b$)$ Standard deviation of the quarterly cash flows.

$($c$)$ As of March $2021,$ Verizon had available cash and short$-$term investments of $$10,205$ million. Calculate lambda and the probability of illiquidity.

$($d$)$ In addition to the available cash and short$-$term investments mentioned in part $($c$),$ Verizon has a credit line of $$9,500$ million. Calculate lambda and the probability of liquidity when this credit line is included.