Five equal charges Q=2 C are equally spaced on a semicircle of radius R=8 cm as

Five equal charges Q=2 C are equally spaced on a semicircle of radius R=8 cm as shown in the Figure. Calculate the force on a charge q=9 C located at the center of the semicircle. (Your result must be in multiples of 1013 Newtons. That means if you get a result of a 9.2 x 1013 just type 9.2 in the answer box. Include 1 digit after the decimal point and maximum of 5% of error is accepted in your answer. Take k=9x109. )