The formula for electric flux is as follows:
Electric flux = E*A (* E = electric field, A = area)
and if electric flux is at an angle from the normal (which is perpendicular) the formula is:
Electric flux = E*A*cos(theta) (* E = electric field, A = area, theta = angle between the normal of E and A)
So for part A, the field is perpendicular so we use the first formula.
Electric flux = E*A
E = 6.35 105 N/C
A = 2.60 m2
Now plug in the values into the formula.
Electric flux = 6.35 105 N/C * 2.60 m2 = 1651000 N · m2/C
Electric flux = 1651000 N · m2/C
Part B, the electric field is parallel, so it is at an angle of 90 from the normal.
So use the second formula:
Electric flux = E*A*cos(theta)
cos(90) = 0,
so therefore the electric flux will be 0.
Electric flux = 0