why sales tax of cash payments is excluded in the option

the following transactions took place during Alan’s first month of trading: Credit sales of $121,000 exclusive of sales tax Credit purchases of $157,110 inclusive of sales tax Cash payments to credit suppliers of $82,710 inclusive of sales tax All transactions are subject to sales tax at 20%. What was the balance on Alan’s sales tax account at the end of his first month of trading? A $1,985 DR B $1,985 CR C $15,770 DR D $15,770 CR answer is A why cash payments to credit suppliers inclusive of sales tax excluded in the answer