d^2u/dt -k(1-u^2)du/dt+au = 0
u(0)=2 (dimensionless); du/dt (0)=0
(a) With 𝑘𝑘 = 1.0 s-1, determine the value of 𝑎𝑎 that would give a heart rate of 1.25 beats/second and Graphically display 𝑢𝑢(t) for this value of 𝑎𝑎 and 0 ≤ t≤ 5 𝑠𝑠 . (25 points).
(b) Graphically display 𝑢𝑢(t) for your chosen values 𝑘𝑘 and 𝑎𝑎 and 0 ≤ t ≤ 5 𝑠𝑠 . Interpret the results.