How many continents do have in africa​

lf u mean countries there are 54 countries

hope it helps

contient=7

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.