Refer attached image
There are be two type of locks 5 digit and 6 digit

5-Digit Locks
Each of the places can be filled using any of the 26 alphabets or the 10 digits so 36 possibilities for 1st place
Similarly, we have 36 possibilities for remaining 4 places
So, total number of 5 digit locks = 36*36*36*36*36 = \(36^5\)

6-Digit Locks
Each of the places can be filled using any of the 26 alphabets or the 10 digits so 36 possibilities for 1st place
Similarly, we have 36 possibilities for remaining 5 places
So, total number of 5 digit locks = 36*36*36*36*36*36 = \(36^6\)

Total possibilities = \(36^5\) + \(36^6\) = \(36^5\) + 36*\(36^5\) = \(36^5\)(1+36) = 37*\(36^5\)

So, answer will be C
Hope it helps!