Can anyone solve this?

How many critical points does the function f ( ) - 4sin- (7x) have on the interval (0, 7)? Provide the x- coordinate for each of the first 2 critical points below in increasing order. Note that the interval does not include 0 or TT. Include a multiplication sign between terms (e g. 3*x). Type Pi for 7. Number of critical points: Number First critical point: b sin (a) ? Second critical point ? lab sin (a)