Help me find the answer please??

Dear student,
   I am giving solution for first three questions for remaining questions kindly ask in another thread 

$$\begin{gathered} a. Diameter of hole is 7 cm \\ Radius of hole =\frac{7}{2}=3.5 cm \\ height of hole =5cm ( from figure ) \\ Curved surface area of hole =2\pi rh \\ =2x \frac{22}{7}x3.5x5 \\ =110 c{m}^2 \\ b. Total surface area of cuboid block= 2(lb+bh+hl) \\ =2(15x10+10x5+5x15) \\ =550 c{m}^2 \\ c. Area of two circular bases =2\left(\pi r^2\right) \\ =2(\frac{22}{7}x3.5^2) c{m}^2 \\ =77 c{m}^2 \end{gathered}$$
Looking forward to hear from you soon
Regards