1200/X

+ 10 = 1500/ 1.2X

X=5

1.2X=6

1200÷

5=240,

1500÷

6=250

1200×(7-5)=2400 yuan (earned for the first time)

200×(7-6)=200 yuan,

7×40%=2.8 yuan

(250-200)×(6-2.8)= 160 yuan,

2400+200- 160=2440 yuan

All in all, these two books earned 2440 yuan.