The reaction of a compound P with  $C{H}_{3}MgBr$  (excess) in  ${\left(C_2{H}_5\right)}_{2}O$  followed by addition of   $H_{2}O$  gives Q. The compound Q on treatment with  $H_{2}S{O}_4$  at   $0^{0}C$ gives R. The reaction of R with $C{H}_{3}COCl$   in the presence of anhydrous  $AlC{l}_3$ ,  $C{H}_{2}C{l}_2$ followed by treatment with $H_{2}O$  produces compound S. [Et in compound P is ethyl group]