4. Draw bifurcation diagrams for the following systems depending on the parameter a. Indi- cate a standard name for each of the observed bifurcations. (a) + = -213 - -0 -2. [5] (b) + = (x - 20 )(r' + 1 -1+0). [6] (c) = = = (1 + 0 - sinhs). 14) (d) r = (a+ a'- 2)r- r', y= 1+r. where r, 4 are polar coordinates. (c) +1 = 0 - 1 + cosh s. =at a- 12