$($a$)$ Would you expect $a>0$ or What about b $?$

You would expect a

$0$ and $b$

$($b$)$ To fit the values of a and $b,$ consider the following data.

A patient with BMI of $20,$ and who does $60$ min of activity each day,

has risk index $h=10.$

A patient with BMI of $10,$ and who does $10$ min of activity each day,

has risk index $h=35.$

Use these data to estimate the values of a and $b.$

Use the data to write a system of linear equations.

$=10$

$=35$

$($Use integers or decimals for any numbers in the expressions.$)$