area of a circle = PI x r^2
you state pi = 3.19 ( it is usually 3.14, if it is a typo see below )
diameter = 14cm
r = 1/2 the diameter, so r = 7 cm
area = 3.19 x 7^2
area = 3.19 x 49 = 156.31 square cm
( if PI = 3.14, area = 3.14 * 49 = 153.86 square cm)