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Explanation:
We'll plug those items into the formula below.
L = loan amount
L = P*( (1+i)^n - 1)/( i*(1+i)^n )
L = 700*( (1+1/600)^360 - 1 )/( 1/600*(1+1/600)^360 )
L = 189,383.961539639
L = 189,383.96
The couple can afford to borrow at most $189,383.96