A) 125
B) 216
C) 294
D) 343
Correct Answer: C
$ \Rightarrow $ $ 4^{3}+5^{3}+6^{3}-62=a^{3} $
$ \Rightarrow $ $ a^{3}=64+125+216-62 $
$ \Rightarrow $ $ a^{3}=343 $
$ \Rightarrow $ $ a=7cm $
$ \therefore $ The whole surface area of newly formed cube $ =6a^{2}=6\times 49=294,cm^{2} $