$2-3.$ Consider the situation of the reflection of a pulse at the interface of two string described in the previous problem. In addition to the net disturbances being equal at the junction, the slope of the net disturbances must also be equal at the junction at all times. Given that ${}_1=4\mathrm{.}0\frac{g}{m},{}_2=9\mathrm{.}0\frac{g}{m}$ and $A_i=0\mathrm{.}50cm$ find $2.A_r($Answer: $-0\mathrm{.}10$ cm $)$ and $3.A_t.($Answer: $0\mathrm{.}40$ cm $)$