If the product of four unequal integers a, B, C and D is equal to 25, then a + B + C + B=

If the product of four unequal integers a, B, C and D is equal to 25, then a + B + C + B=

Because ABCD is an integer
So according to 25 = 5 * 5 = 1 * 1 * 5 * 5
1 = 1 * 1 or - 1 * - 1
5 = 1 * 5 or - 1 * - 5
So 25 = - 1 * - 5 * 1 * 5
Then a + B + C + D = - 1 + 1-5 + 5 = 0

If a.b.c.d.e.f is six rational numbers, and a / b = 1 / 2, B / C = - 1 / 3, C / D = 1 / 4, D / E = - 1 / 5, f / A=____ Thank you

If a.b.c.d.e.f is six rational numbers, and a / b = 1 / 2, B / C = - 1 / 3, C / D = 1 / 4, D / E = - 1 / 5, (less E / F = 1 / 6), f / A=____
Multiplication of five forms
a/b×b/c×c/d×d/e×e/f
=1/2×(-1/3)×1/4×(-1/5)×(1/6)
=1/120×?
That is, a / F = 1 / 720
So f / a = 720

4.7-(8.9)-7.5＋（-6）,

4.7-(8.9)-7.5＋（-6）
=4.7-8.9-7.5-6
=-17.7