Let the number of red, black, green and blue balls be R, B, G, U respectively.
B=R (There are as many black balls as red balls)
G+R=10 so G=10-R (Green balls and red balls should add up to 10)
R+10=U (There should be 10 more blue balls than red balls)
The minimal number of balls is 2, 304 so we have the following inequality:
R+B+G+U≥ 2,304
R+(R)+(10-R)+ (R+10)≥2,304
4R≥2,304
R≥2,304/4=576 so R=576
Answer: 576