There is a grass field. The grass has its original height of 2 cm, and its speed of growth is...

There is a grass field. The grass has its original height of 2 cm, and its speed of growth is 0.05y. After 10 days, we start to put fertilizers on the grass field everyday, now, the growth speed of the grass is 0.05y+ kb(t). After t days, what is the amount of the grass?

1. Let k1b(t)= 0.2(t-10)

y(0)=2

dy/dt=0.05y+U10(t)* 0.2(t-10)

dy/dt={ 0.05 y,      0≤t≤10

{ 0.05y +0.2(t-10), t≥10   t∈ℤ

2. Let k2b(t)= 0.1e0.1(t-10)

y(0)=2

dy/dt=0.05y+U10(t)* 0.1e0.1(t-10)

dy/dt={ 0.05 y, 0≤t≤10

       { 0.05y+ 0.1e0.1(t-10),  t≥10   t∈ℤ