Apple trees need 5 square feet and Cherry trees need 4 square feet and you have 100 square feet in total:
---> 5A + 4C ≤ 100 , the first and last have that (your choice is out)
Apple trees cost $40 each, and Cherry trees cost $50 each and you have $1000 in total to spend:
50A + 40C ≤ 1000
Which answer fits both conditions ?