index=0;
time_axis=0:0.1:25; %i chose time step as 0.1 seconds
speed=zeros(1, numel(time_axis)); %this line is for memory allocation, its optional
for t=0:0.1:25 %we could also use a while loop on time_axis elements
index=index+1;
if t<5
speed(index)= 0.1553567*t^6-2.0416*t^5 ... %complete the formula
elseif t<15.4
speed(index)=0.0039.... %complete the formula
else
speed(index)=.... %complete the formula
end
end
plot(time_axis,speed); %you can use xlabel, ylabel and title functions to write labels