Part B

In this part, you will write a function that computes the shipping cost, given the weight of the package.

$$ If $0<$ weight $<=1\mathrm{.}0,$ return $$3\mathrm{.}50$

$$ If $1\mathrm{.}0<$ weight $<=3\mathrm{.}0,$ return $$5\mathrm{.}50$

$$ If $3\mathrm{.}0<$ weight $<=10\mathrm{.}0,$ return $$8\mathrm{.}50$

$$ If $10\mathrm{.}0<$ weight $<=20\mathrm{.}0,$ return $$10\mathrm{.}50$

$$ If $10\mathrm{.}0<$ weight $<=20\mathrm{.}0,$ return $$10\mathrm{.}50$

$$ If weight is invalid, return $-1.$