please show steps $($dont use excel$)$

A firm has estimated that it will need $$3\mathrm{.}3$ million net cash during the year. Current interest rate on money market securities is $3\mathrm{.}40\%$ per year and the cost of buying and selling securities is $$28\mathrm{.}10$ per transaction. What is the optimal transaction size of securities$?$

a$.$

$$56,812$

b$.$

$$13,848$

c$.$

$$13,393$

d$.$

$$52,224$

e$.$

$$73,856$

The answer is not d