$4.$ You are planning to purchase a call option on the common stock of Company X$.$ The price of the call option will be higher, all else equal, if:

a$.$ The option expires in two months rather than eight months

b$.$ The risk$-$free rate is $3\%$ rather than $5\%$

c$.$ The standard deviation of returns for Company X is $0\mathrm{.}200$ rather than $0\mathrm{.}500$

d$.$ The strike price is $$40$ rather than $$30$

e$.$ The option expires in six months rather than three months