Therule of 70and theruleof72give rough estimates of the number of years it would take for a certain variable to double. When using therule of 70, the number70is used in the calculation. Likewise, when using theruleof72, the number72is used in the calculation, According to the rule 70 and 72, if a 10% annual increase in real GDP would lead to a doubling of real GDP in how many years? Use the rule 70 and 72 calculation. (use separate calculations)