The profit of a B brand electric motorcycle is 3500-3000=500 yuan.
If you buy X electric motorcycles of brand A, buy 40-X electric motorcycles of brand B..
4000 X+3000(40-X)& lt； 140000
1000X+500(40-X)>29000
18
That is, X= 18, 19 or 20.
(1) When buying A brand electric motorcycles 18, buy 22 B brand electric motorcycles.
The actual purchase price is18 * 4000+22 * 3000 = 72000+66000 =138000 yuan.
Actual profit18 *1000+22 * 500 =18000+1000 = 29000 yuan.
(2) When A brand electric motorcycle purchases 19, B brand electric motorcycle purchases 2 1.
The actual purchase price is19 * 4000+21* 3000 = 76000+63000 =139000 yuan.
Actual profit19 *1000+21* 500 =19000+10500 = 29500 yuan.
(3) When buying 20 A brand electric motorcycles, buy 20 B brand electric motorcycles.
The actual purchase price is 20 * 4000+20 * 3000 = 80000+60000 =140000 yuan.
The actual profit is 20 *1000+20 * 500 = 20000+10000 = 30000 yuan.
Comparison (1)(2)(3)
When shopping malls buy 20 A brand electric motorcycles, the profit is the biggest, with a maximum profit of 30,000 yuan.