By building its own shipping and delivery infrastructure, Amazon saves about costs, and "click to door" delivery time was nearly in third$-$party shipping

a$.25\%$ in third party shipping costs and $3$ days better days better than the industry.

b$.25\%$ in third party shipping costs and $4$ days better

c$.33\%$ in third party shipping costs and $3$ days better

d$.33\%$ in third party shipping costs and $2$ days better

e$.15\%$ in third party shipping costs and $4$ days better