For a given stress level, by how much would the minimum creep rate in aluminum be expected to increase if the test temperature were increased from $550$ to $750$ K$?($consider temperature dependence of creep rate$)$

FIGURE $5\mathrm{.}8$ Variation of apparent activation energy for creep in aluminum as a function of temperature. $($From O$.$ D$.$ Sherby, J$.$ L$.$ Lytton, and J$.$ E$.$ Dorn, ${?}^{13}$ reprinted with permission from Sherby and Pergamon Press, Elmsford, NY$,1957.)$