Can someone solve this?
I have done part (a).
Need help with (b)and(c)

The pyramid below was dissected by a horizontal plane which shape describes the pyramid horizontal cross section

Last month, a 770 g box of cereal was sold at a grocery store for $3.10. however, this month, the cereal manufacturer launched the same cereal in a 640 g box, which is being sold at $2.50. what is the percent change in the unit price?

Reinel saves 30% of every pay check. his paycheck last week was 560$. how much did reniel save last week?