Below y(t) for the motion of a mass-spring system are given. Calculate all moments of time t>0 when it passes through the equilibrium. How many times it will happen?
a. y(t) = 2e⁻²ᵗ-5e⁻⁴ᵗ
b. y(t) = 2e⁻²ᵗ+5e⁻⁴ᵗ
c. y(t) = 5e⁻⁴ᵗ+2e⁻²ᵗ
d. y(t) = 2e⁻²ᵗ-3e⁻²ᵗ
e. y(t) = 2e⁻²ᵗ+3e⁻²ᵗ