#### Answer

$a). (3)\, less \,than\, 190\, mi/hr$
$b). 187.3mi/hr.$

#### Work Step by Step

a).Average speed will be (3) less than 190 mi/hr.
Since, average speed is (Total distance travelled / Total time taken), it will be less than just the average of the speeds.
b). Total distance = $2.5 \times 4= 10 mi$
Total time = $(\frac{2.5}{160}+\frac{2.5}{180}+\frac{2.5}{200}+\frac{2.5}{220}) hrs.$
So, Average speed =$\frac{Total \,distance}{Total\, time}=187.3 mi/hr $