The radius of curvature of the left and right surface of the concave lens are 10 cm and 15 cm respectively. The radius of curvature of the mirror is 15 cm

−1F=P=2Pl1+2Pl2+Pm………….(1)P11=1f1=(μ−1)1R1−1R2PL1=(1.5−1]−110−115=−112…(2)PL2=1f2=(μ−1)1R1−1R2Pl2=43−1215=245…………(3)Pm=−1f=+215………………..(4)−1F=P=2−112+245+215=−16+445+215=118F = -18cm. Focus is negative means system will behave as concave mirror.