I think the answer is Wednesday.
We know that :
Mon=80, Tu=30, wed=100, thu=120, fri=70
So if we sum up we can conclude that the total number is 400:
And also we know that a circle is 360°.
Monday occupies: 80/400÷X/360 -->X=72° of the circle.
Sunday Tuesday occupies:3/40÷X/360
And you can calculate the rest of the days like this.
We understand based on the piechart that none of the days shown occupy 90° or exactly 1/4 of the circle.
Thank you so much … I forgot to think it from the degree of the circle