In a leap year, total number of days = 366 days.

In 366 days, there are 52 weeks and 2 days.

Now two days may be

(i) Sunday and Monday

(ii) Monday and Tuesday

(iii) Tuesday and Wednesday

(iv) Wednesday and Thursday

(v) Thursday and Friday

(vi) Friday and Saturday

(vii) Saturday and Sunday

Now in total 7 possibilities, Sunday and Monday both come together is 1 time.

So probabilities of 53 Sunday and Monday in a leap year = 1/7