the table shows the opening and closing rent receivable acco

the table shows the opening and closing rent receivable account balances:
$ start of year end of year
rent received in advance 4200 1600
rent due in arrears 2000 2400
during the year,$111 000 rent income was received ,what is the rent receivable for the year?
a 110 600
b 111 000
c 112 000
d 114 000
但为什么呢,