Question

I need help for the solution​

Answer 1

`\boxed{ \ dY_t=(2\theta+2\psi Y_t+\phi^2)dt+2\phi √(Y_t)dW_t\ }`

Explanation:

it is a long time I have not applied Ito's lemma

I would say the following

for
`f(x)=x^2`

f'(x)=2x

f''(x)=2

so using Ito's lemma we can write that

`dY_t=2V_tdV_t+\phi^2dt`

`dY_t=2(\theta+\psi V_t^2)dt+2\phi V_tdW_t+\phi^2dt`

`dY_t=(2\theta+2\psi V_t^2+\phi^2)dt+2\phi V_tdW_t`

so it comes

`dY_t=(2\theta+2\psi Y_t+\phi^2)dt+2\phi √(Y_t)dW_t`