Wires \[A\] and \[B\] are connected with blocks \[P\] and \[Q\], as shown. The ratio of lengths, radii and Young's modulus of wires \[A\] and \[B\] are \[r,\,2r\] and 3r respectively (\[r\] is a constant). Find the mass of block \[P\] if ratio of increase in their corresponding lengths is \[\frac{1}{6{{r}^{2}}}\]. The mass of the block \[Q\] is 3\[M\]

• A. \[M\]               
• B. \[3M\]
• C. \[6M\]              
• D. \[9M\]