Konsider a program takes $10$ s running on a single processor. if $60\%$ of the execution time involves code that is inherently serial and a fraction $40\%$ that involves code that is infinitely paralielizable with no scheduling overhead. then the speedup of executing this program on $5$ cores processor is equals to:

a$.0\mathrm{.}68$

b$.5\mathrm{.}1$

c$.6\mathrm{.}8$

d$.1\mathrm{.}47$