Solution:Formula for calculating day of any date
0 = sunday, 1 = monday.... 6 = saturday
A = century code (4, 2 ,0 ,6 for remainder
1, 2, 3, 0) dividing by first two digit of the year by 4
B = last two digits of year
C = number of leap years fallen in that century before that date.
D = month code (respective code of the months are 0, 3, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5)
E = date
Day = remainder of (A + B + C + D + E) when divided by 7.
Here we have to find sunday in february 2020 so firstly we will find the day on 1
february 2020
So For 1 february 2020
A = 6, B = 20, C = 4, D = 3, E = 1
According to formula,

=34/7 is 6, 6 stands for saturday .
So day on 1 february 2020 = saturday
So day on 2 february 2020 = saturday + 1 = sunday Hence sunday comes on 2, 9, 16 and 23 in february 2020.