How to extend exponential fitted line to extrapolate values

I made the code below to graph results I got doing some viscosity testing. I want to use the results to predict how much water to add to some paint to get to a given viscosity. I need to extend the line of best fit to the around the 70% mark on the x axis. My knowledge of matlab is pretty basic as you can probably tell.

T = readtable('ViscosityResults.xlsx','Range','L2:M14',... #read spreadsheet and select range
    'ReadVariableNames',true,'VariableNamingRule','preserve')...#take headings from file and keep them as they are


figure;
x = T{:,1}
y = T{:,2}
f = fit(x,y,'exp1');
plot(f,x,y)
xlim([0,70])
ylim([0,45])
title('Viscosity of primer by % volume water')
xlabel('% Volume water')
ylabel('Viscosity (cP)')

I just want a matlab graph that basically looks like this, with the extended trendline:

Answer 1

[Matt J]

xx=linspace(0,85,500);

plot(xx,f(xx))

[Daniel Jordan]

Thanks for your help!