Factor común por agrupación de términos 4a3-1-a2+4a

According to the number line, what is the distance between points a and b? v ++ + + + + -16 -14 -12 -10 -8 + 6 + 4 + -2 + 0 + 2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 o6 units o 7 units 12 units o 14 units

Can someone me and plz do the problem

Eric has challenged himself to walk 24,000 steps in 4 days. if eric walks the same number of steps each day, which function represents the number of steps eric still needs to walk to reach his goal with respect to the number of days since he started his challenge? a. y = 8,000x − 24,000 b. y = -8,000x + 24,000 c. y = 6,000x − 24,000 d. y = -6,000x + 24,000