You can
put this solution on YOUR website!at the middle of the arch, x=50 and y=20
20=50k(50-100) __ 20=50k(-50) __ dividing by -2500 __ -.008=k
a 40 ft wide object would pass through between x=30 and x=70
__ the clearance is y=(-.008)30(-70) __ y=16.8
__ the object fits through