Parabolic arch rib, $20$m span and $3$m rise is hinged at the abutments and the crown and carries a point load of $10$kN at

$7\mathrm{.}5$m from the left$-$hand hinge. Calculate the horizontal thrust and the bending moment at a section $7\mathrm{.}5$m from right$-$hand

hinge. What is the value of the greatest bending moment in the arch and where does it occur.