#### Answer

a. $y=0.8+0.45x$
b. $y=2.6+0.15x$
c. $6$ weeks, $3.5$ symptoms for each group; intersection point $(6,3.5)$.

#### Work Step by Step

a. Based on the given conditions, we can write the function as $y=0.8+0.45x$
b. Similarly, based on the given conditions, we can write this function as $y=2.6+0.15x$
c. Let $0.8+0.45x=2.6+0.15x$; we have $0.3x=1.8$ and $x=6$ weeks. At $x=6$, we have $y=0.8+0.45(6)=3.5$ symptoms for each group. These results are shown in the corresponding figure as the intersection point $(6,3.5)$.