<span> $70 / 9 = $7.78
answer
</span><span>$7.78 hourly</span>
The cost of the 15 percent of replaced vacuum cleaner which are sold under warranty is $3,681,384. Option b is correct.
<h3>What is percentage ?</h3>
Percentage of a number is the part of the number expressed in the in every hundred. Percentage of a number is expressed with the symbol '%'.
A vacuum cleaner costs $68, and the full-replacement extended warranty costs $22.
The manufacturer sells 360,920 vacuum cleaners under warranty and must replace 15% of them to honor the warranties. Thus, the number of vecuum cleaner replaced by manufacturer is,

The cost of one vacuum cleaner is $68. Thus the cost of 54138 vcacuum cleaner is,

Hence, the cost of the 15 percent of replaced vacuum cleaner which are sold under warranty is $3,681,384. Option b is correct.
Learn more about the percentage here;
brainly.com/question/24304697
Hint: substitute 2^x by say 't': t = 2^x, then you'll have an inequality with a second order polynomial (2/t-4*t<7--> ...). In the end something like t^2 + a*t+b > 0, for some values of a and b, find the roots and get the intervals where it is satisfied.
It equals to 65 for the exact answer