Task 1.

Implement the function to find the combination of 4 digits in a row which gives the max multiplication. If object is not a string or there are no combinations found - return nil. If combination is found - return it's multiplication result.
E.g.

max_multiplication('abc12345def') => 120 # 2*3*4*5
max_multiplication('a1b2c3d4e') => nil

Task 2.

Implement the function to sort array of numbers by amount of '1' in its binary representation. Numbers with identical amount of '1's should be ordered by decimal representation.
E.g.

# 3 = 11, 7 = 111, 8 = 1000, 9 = 1001.
sort([3,7,8,9]) => [8,3,9,7] # 1000, 11, 1001, 111