Put the sentences below in the correct order to make a main body paragraph. Which is the topic sentence? Which sentences support it?

С=3а
b=a-6.8
a+(a-6.8)+3a=43.2
a+a-6.8+3a=43.2
5a-6.8=43.2
5a=43.2+6.8
5a=50
a=10
b=10-6.8=3.2
c=3*10=30
V=abc=10*3.2*30=960 см³