an><span class='hljl-n'>p</span><span class='hljl-t'>
    </span><span class='hljl-n'>N</span><span class='hljl-t'> </span><span class='hljl-oB'>=</span><span class='hljl-t'> </span><span class='hljl-n'>S</span><span class='hljl-oB'>+</span><span class='hljl-n'>I</span><span class='hljl-oB'>+</span><span class='hljl-n'>R</span><span class='hljl-t'>
    </span><span class='hljl-n'>ifrac</span><span class='hljl-t'> </span><span class='hljl-oB'>=</span><span class='hljl-t'> </span><span class='hljl-n'>β</span