Answer:
a)The total amount of her  weekly stock sales  = $7,200
b) The total amount of her yearly stock sales  = $350,000
Step-by-step explanation:
(a)  Let us assume that the total a mount of her sales in a week  = $m
   Commission earned in a week = $288
   Now, 4 % of her total sales  = $288
   or, 4% of ($m)  = $288
  ⇒[tex]\frac{4}{100}  \times  m = 288[/tex]
   or, [tex]m = \frac{288 \times 100}{4}  = 7,200[/tex]
   ⇒ m = $7,200
Hence, the total amount of her  weekly stock sales  = $7,200
b)  Let us assume that the total amount of her sales in a year  = $k
   The total amount of commission earned  = $14,000
Now, 4 % of her total sales  = $14,000
   or, 4% of ($k)  = $14,000
  ⇒[tex]\frac{4}{100}  \times  k = 14,000[/tex]
   or, [tex]k = \frac{14,000 \times 100}{4}  = 350,000[/tex]
   ⇒ k = $350,000
Hence, the total amount of her yearly stock sales  = $350,000
