For four years, Mary Thomas invested $$4,200$ each year in America Bank stock. The stock was selling for $$62$ in $2018,$ for $$58$ in

$2019,$ for $$59$ in $2020,$ and for $$51$ in $2021.$

a$.$ What is Mary's total investment in America Bank?

b$.$ After four years, how many shares does Mary own?

Note: Round your intermediate calculations to $1$ decimal place. Round up your final answer to the nearest whole unit.

c$.$ What is the average cost per share of Mary's investment?

Note: Round up your intermediate value of "Total shares" to the nearest whole unit. Round your final answer to $2$ decimal

places.