If income per day is less than $2, then we can take $2 as the maximum value.
(a) total combined income will be: 2.4 billion x $2 = $4.8 billion
(b) Percentage of world's total income will be: 4.8 billion/75 trillion x 100
4.8 x 10^7/ 75 x10^13 = 0.064 x 10 ^ -6
6.4 x 10 ^ -4 x 100