If the acceleration was constant, then it would be the same as the average acceleration over the 10 second interval:
[tex]a=\dfrac{v-v_0}{\Delta t}\implies a=\dfrac{29\,\frac{\mathrm m}{\mathrm s}-27\,\frac{\mathrm m}{\mathrm s}}{10\,\mathrm s}=0.20\,\dfrac{\mathrm m}{\mathrm s^2}[/tex]