The terms $1/20,$ n$/45$ means the $\_\_\_\_\_\_.$

Multiple choice question.

buyer will receive a $1\%$ discount if payment is made within $45$ days; otherwise the full payment is due in $20$ days

full payment is due in $20$ days and any payment after $45$ will be assessed a $2\%$ penalty

buyer will receive a $1\%$ discount if payment is made within $20$ days; otherwise the full payment is due in $45$ days

full payment is due in $45$ days and a $1\%$ penalty will be charged for every $20$ day period afterward