Solve one of the following two cryptarithmetic problem $($if you select to solve

$($b$)$ there is $20$ point bonus if you solve it correctly$)$:

$($a$)$ FOUR$+$ONE $=$FIVE by hand using the strategy of backtracking with forward

checking. The letters can only represent digits $0$ to $9,$ each letter maps to one and

only one number, and each number maps to one and only one number.

$($b$)(+20$ Bonus Points$)$ TWELVE$-$:SIX $=$ TWO by hand using the strategy of back$-$

tracking with forward checking. The letters can only represent digits $0$ to $9,$ each

letter maps to one and only one number, and each number maps to one and only

one number.